This invention concerns snowshoes, particularly snowshoes of molded plastic or composite material, and the invention encompasses a molded snowshoe with improved ability to adapt to uneven terrain.
Traction and stability on a varied terrain are valuable attributes for a snowshoe. One way to allow enhanced traction and stability is to provide a snowshoe structure which can adapt to various surface contours to effect better contact with the surface, and thus enhanced traction and stability. This invention provides a structure with improved ability to adapt to and make contact with the snow or ice surface on which the snowshoe is used.
Typical snowshoes provide flotation, traction and stability by the incorporation of flotation means (primarily a deck), traction means (cleats or rails), and a means to attach the user's foot to a relatively rigid structure (a boot binding).
The traditional frame based snowshoe has a peripheral framed structure that is essentially rigid. This is required to suspend and support the traditional flotation surfaces that consist of flexible members such as rawhide strips, coated fabrics or thin plastic sheets. Traction elements are attached to the underside of this construction for improved traction on ice and snow surfaces. A binding of some type is attached to the structure to receive the user's foot. The traditional framed snowshoe construction thus teaches the need for a rigid frame surrounding the periphery of the snowshoe, and a flexible decking material suspended within the frame. The flexible decking is inherently too flexible to bear the flotation loads of the snowshoe without the support of the peripheral frame.
It can be advantageous with such a construction to allow the traction elements attached to the snowshoe structure to conform to the contours of the snow and ice surface by providing some level of relative flexibility or suspension from the generally rigid structure of the snowshoe. The flexible decking snowshoe suspends some traction elements on the deck, and suspends the binding (with toe cleat) somewhat, and thus adapts to some extent to the terrain. Other prior approaches using this concept include the use of various suspension systems such as in K2 Snowshoes U.S. Pat. No. 6,898,874, which provides adaptation to side terrain. There have been other approaches for suspending the snowshoe binding and the traction elements attached to the underside of the snowshoe bindings, which allow some degree of relative motion or flexibility between the overall snowshoe structure and the binding with its attached traction means.
More recently, constructions of snowshoes have been developed that consist of flotation surfaces formed of materials such as injection molded plastic, of a thickness and stiffness such as not to require peripheral frames to help resist and support the flotation loads associated with snowshoeing. One such prior art example can be found in the MSR Denali model snowshoe made of a molded one piece surface comprising the flotation surface of the snowshoe. Additional structure is provided in the form of two steel rails running longitudinally along the lower side of the molded decking surface, which also serve as traction elements. This prior art teaches the importance of structural rigidity through the combination of the structure of the longitudinal metal rails, along with structural channels molded into the decking structure of the snowshoe. See, for example, MSR U.S. Pat. Nos. 5,469,643, 5,517,773 and 5,921,007.
In the described MSR snowshoe, the binding of the snowshoe was attached to the longitudinal traction rails in a pivoting fashion. A certain degree of structural flexibility of the overall structure is obtained by this arrangement. However, the structural rigidity of this construction is also somewhat limiting on the degree to which the structure can conform to the underlying contours. Further, the need to use one material for the entire deck surface for such constructions can be a limitation in the selection of materials to meet the various requirements of the snowshoe structure.
The above are examples of ways in which the prior art has achieved the required flotation and structure required of a snowshoe combined with contact and traction with the underlying terrain surface.
The prior art also discloses a compound deck snowshoe, with an additional piece of deck structure or “tail extender” that can be added or taken off the snowshoe body by the user, as a means to alter the degree of flotation of the snowshoe, as in U.S. Pat. Nos. 5,517,773 and 6,195,919; see also U.S. Pat. Nos. 6,006,453 and 6,226,899. While such prior art does disclose a deck comprised of two or more pieces, it does not teach any method for substantially affecting the overall structural flexibility of the snowshoe structure, for adaptation to terrain. Further, the loads that can be imparted into the second decking section in U.S. Pat. No. 6,195,919 are limited by the absence of any substantial structural member spanning the mating region.
There is a need for a molded or composite snowshoe that has a deck rigidity sufficient for the needed flotation while also affording a torsional (warping) flexibility that allows the traction elements or cleats on the snowshoe bottom to contact uneven terrain.